iommu/mediatek: Use a u32 flags to describe different HW features

Given the fact that we are adding more and more plat_data bool values,
it would make sense to use a u32 flags register and add the appropriate
macro definitions to set and check for a flag present.
No functional change.

Suggested-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Chao Hao <chao.hao@mediatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Yong Wu <yong.wu@mediatek.com>
Link: https://lore.kernel.org/r/20200703044127.27438-4-chao.hao@mediatek.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>